Machine for forming gears



April 18, 1944. H. PELPHREY u MACHINE FOR FORMING GEARS vFiled Oct. 29,1940 4 Sheets-Sheet l INVENTOR Hal April 18, 1944. PELPHREY I 2,346,867

` MACHINE FOR FORMING GEARS Filed Oct. 29, 17940 4 Sheets-Sheet 2NVENTOR H4 )arg Z/P feg.

ATTORN 5,

April 18, 1944. H, PELPHREY 2,346,867

MACHINE FOR FORMING GEARs y Filed oct. 29, 1940 4 sheets-sheet 3 Www/WWApril 18, 1944. H. PELPHREY MACHINE FOR FORMING GEARS 4' sheets-sheet 4Filed oct. 29, 1940 INVENTOR /drf'g BZyrecg BY Ma?? alla ATTORN 5.

Patented Apr. 18, '1944 UNITED STATES PATENT OFFICE MACHINE Foa FonMlNGomas v Harry Pelphrey, Detroit, Mich., assigner to Michigan ToolCompany, Detroit, Mich., a corpol'ation of Delaware Application October29, 1940, Serial No. 383,331

16 Claims.

The present invention relates to machines for forming machine elementssuch as gears.

' One of the primary objects of the present invention is to provideimproved machines of the type mentioned by means of which all of theteeth of a gear may be` simultaneously formed on a gear blank, therebygreatly increasing the V speed of production of such gears.

Another object of the invention is to provide an improved cutterheadassembly for use teeth of a helical gear may be simultaneously formed inan improved manner.

Another object of the invention is to provide an improved constructionin which a plurality of circumferentially spaced, radially disposedcutmounted thereon are reciprocated with respect to each other, and inwhichone of the reciprocating elements is guided on the 1'ielix of theteeth being cut.

v ters and a work holder having a gear blank Other objects of theinvention will become apparent from the following specification, thedrawings relating thereto, and the claims hereinafter set forth.

In the drawings, in which like numerals are used to designate like viewsthroughout:

Figure 1 is a perspective view of a gear form- .ing machine according tothe present inven- ,along the line 4-4 of Fig. 2;

Fig. 5 is an enlarged, vertical cross-sectional view of the cutterheadhaving the cutters mounted therein, together with the assembly forradially moving the cutters;

Fig. 6 is a fragmentary cross-sectional view, taken substantially alongthe line 8-8 of Fig. 5;

-Fig. 7 is a fragmentary vertical cross-sectional view,*takensubstantially along the line 1-1 of Fig. 6:

Fig. 8 is a partial view ysimilar to Fig. 5, showing the parts in adiierent position to retract the cutters with respect to the work;

Fig. 9 is a fragmentary elevational view, taken substantially along theline 9-9 of Fig. 4;

Fig.'10 is a vertical cross-sectional view, taken substantially alongthe line |8-"-IIIl of Fig; 2; and

Fig. 11 is an enlarged cross-sectional fview,

taken substantially'along the. line Il II ofFig.' I

According to the present invention, a construe# tion is provided inv'which a plurality of circumferentially spaced, radially disposedcutters are mounted inv a. cutterhead in `surrounding relationship to agear blank. Such gear blankis mounted upon a reciprocating plunger `andupon upward movement of such plunger the gear blank is moved intocutting engagement with the cutters. The cutters are alternately-fedradiallyinwardly and backed-ot! duringthe upward and downward strokes,respectively, of the gear blank, so that as the cutters are fed inwardlyall of the gear teeth are formed simultaneously. The

cutters are of such a shape'that in the completed operationv they removeentirely the interdental stock between the teeth formed thereby.

In the particular embodiment illustrated, the machine is designed forcutting helical gears,

and in order to accomplish this the present inven'- tion contemplatesthe mounting of the cutters at an angle to the axis of reciprocation ofthe machine element or gear blank, and such gear blank is rotated withrespect to its axis as Yit is reciprocated. Inorder to effect this, thereciproeating ram upon which the gear blank is mounted is caused torotate upon the helix of the gear to be out."

For a more detailed description ofthe invention, reference'may be had tothe drawings-in which a base or upright standard is generally indicatedat II).` Such standard I0 has a machined vertical front surface I2 uponwhich a vertically adjustable mounting member or head stock element `.I4is slidably mounted. Such member I4 is yslidably mounted to the face I2bylmeansv of lvertically extending gibs, which are xed to the face I2and form ways which engage the vertical side edges' of the member I4.y

The lower and rear end of member I4 isprovided with a vertical -openingI6 therethrough, through which a vertical screw I8 extends. A bearingnut 20 threadably engages the screw I8 and is xed to member I4 inalignment with the lower end of opening I8, so that as the screw I8 isturned the member I4 is raised or lowered with respect to the base I8.

The lower end of screw I8 is mounted within a suitable thrust bearing 22mounted-on standard III,- and has a gear 24 keyed thereto.` A pinionmeshes with gear 24 and is keyed to a suitable pinion shaft 26, which ismounted within suitable bearingasuch as 28, and has a handwheel 38secured to the outer end thereof. -It will thus be evident that by.turning the handwheel 30 the screw I8 is correspondingly -turned toraise or lower the member I4 for the purpose of vertically adjustingsuch member with respect to the base I0.

The gear to be formed is indicated at 32 (Figs. 1, 5, 6 and 8) and, inthe embodiment illustrated. is an external helical gear, in which theteeth are of involute form. The gear may be formed from either a singleblank or from a gear cluster blank, and is mounted upon a mandrel 34having a shoulder portion 36, which bears against the top face of thegear blank 32. The mandrel 34 extends upwardly above the top of the gearblank 32. and is provided with a plurality of longitudinally extendinggrooves 38, which are circumferentially spaced about the periphery ofthe mandrel, so thatcooling fluid may flow downwardly over the gearblank and cutters during the cutting operation. y

The lower end of mandrel 34 (Fig. 10) has an integral andenlargedportion 40, and is received within an aperture 42 of an adapter plate44. The enlarged, or disc-shaped portion 40 is received within a seatformed in the under surface of plate 44. A clamp ring 46 bears againstthe top surface of member 44, and spacer members 48 are disposed betweenthe ring 46 and the underside of the gear blank 32, so that the mandrel,with the gear blank 32 mounted thereon, is accurately fixed with respectto the plate 44 and so that the gear blank 32 cannot turn with respectthereto.

The adapter plate 44 is securely xed to the top surface of a verticallyreciprocating and rotating ram 50. Such ram 50 is slidably disposedWithin the vertical bore of a ram casing 52, which is mounted upon amounting bracket 54. Such mounting bracket 54 has a vertical boretherethrough, through which a casing 52 extends, and is secured to thestandard l by means of bolts 56. The casing 52 is secured to the member54 by means of a plurality of bolts 58.

The ram 50 reciprocates within the casing, and a chip guard 60 is`ilxedly mounted with respect to the plate 44 and ram 50, so that itreciprocates therewith. The member 60 has a skirt portion which slidablyembraces the upper end of casing 52, so that chips cannot fall withinthe casing.

The ram -50 has a depending, axially aligned stem- 62, which terminatesin a ball 64. Such ball seats within a ball cup member 66, which isdisposed within a recess formed in the upper'end of anauxiliary rammember 10. A ball cap in the form of a ring 12 is fixed to the upper endof the auxiliary ram 10 by means of bolts 14, and has an aperturetherethrough through which the stem `62 projects with a portion of themember 12 overlying the ball 64. The auxiliary ram 10 isffmounted withina crank guide 16, whichis mounted to the standard I0 by means ofsuitable bolts 18.

The lower end of auxiliary ram 10 is connected to a connecting rod 80 bymeans of a wrist pin 02, and the lower end of the connecting rod 80 isconnected' to the crank 84 of a crank shaft 86. Such crank shaft ismounted within suitable crank bearings 88 mounted upon standard l0.

The crank shaft 86 is connected to a drive shaft 90 by means of a sleeve82; and the drive shaft 90 is connected through suitable gear reductionmeans S4 with a prime mover in the form of an electric motor 96, bymeans of a belt and pulley arrangement indicated at 38. It will thus beseen that as the prime mover 96 is operated, the crank shaft 86 isrotated to reciprocate the auxiliary ram 10, together with the main ram58.

As the ram 50, together with the gear blank 32, is reciprocated, it isalso turned or rotated with respect to its axis, so that any point onthe periphery of the gear blank follows the path of the helix of thegear to be cut. In order to eiect such a motion, guide means areprovided which include a spiral guide |0|, which is fixed to the stem 62of ram 50 by means of suitable bolts |02. Such rotating guide |0| has aspiral guide surface |04, which has a contour following the helix of thegear to be cut. Complementary spiral guides |05 and |08 are fixed to thecasing 52 by means of suitable bolts |'|0, and are iixed with respect toeach other by means of suitable bolts ||2. The guides |06 and |08 have aspiral guide surface I4, which cooperates with the guide surface ofmember |0| to properly guide the ram 50 as it is rotated andreciprocated upon the helix of the gear to be cut.

It will be appreciated that the guide surface may be formed upon thehelix of the gear to be cut, which may be predetermined, so that a gearhaving any helix, within limits of nine ,inch lead to infinity, may beformed.

In order to form the teeth in the gear blank 32, a plurality ofcircumferentially spaced, radially disposed cutters I6 are mounted tothe head stock element |4 by means of a cutterhead assembly whichincludes means for controllably feeding the cutters ||6 radiallyinwardly and backing such cutters off with respect to the gear blank.Such means are best shown in Figs. 1 through 9.

The cutters ||6 are elongated in form and have a transverse shape whichis that of a rightangle trapezoid. Each of the cutters |I6 has anelongated cutting portion ||8 formed along the inner end edge thereofwith the cutting edge thereof disposed downwardly, asindicated at |20.In transverse section, the cutting portion has a shape corresponding tothe shape of the entire interdental space between the teeth of the gearto be cut. The opposite end edge of the cutter |l|6 slopes upwardly andinwardly, as indicated at |22, and has a surface formed upon the contourof a cone. A transversely extending slot |24 having the sides thereofsubstantially parallel to the end |22,!but transversely, straight, isformed in each of the cutters ||6. For a more complete description ofthe cutters H6, reference may be had to the copending application ofHarry Pelphrey, Serial No. 363,329 illed October 29, 1940,-

in which the cutters per se are disclosed in detail and claimed.

The cutters ||6 are mounted within a plurality of complementary,circumferentially spaced, radially disposed slots |26 formed in acutterhead |28.

The cutterhead |28 has a central bore |30 formed therethrough, and isprovided with an enlarged bottom, or base portion, within which suchslots |26 are formed. The slots |26 are disposed at a predeterminedangle with respect to the axis of reciprocation of the ram and suchangle is the .helix angle of the gear to be cut. The slots in helixangle is preferred so that the cutters may be made as thin ,as possible.According to the broader aspects of the invention, such angle could,

however, be the helix angle on the pitch or base circles; but in suchcases the cutters would necessarily have to be thicker.

A head plate |32, having a central opening |34 therethrough, bearsagainst the under surface of cutterhead |28 and also bears against thebottom surface of cutters ||8, as best shown in Fig. 7, to fix thecutters against axial displacement with respect to the standard. Theplate |32 has a plurality of circumferentially spaced, upwardlyextending tabs or projections |36 on the top surface thereof, which areso shaped that the sides thereof bear against the sides of the cutters||6, as best shown in Fig. 6. 'I'he plate member |32 is` bolted to aforwardly projecting tion |38 which is formed integral member |4.Vertically extendin l also formed integral with the -shaped portion |38,and with the main body portion of the head stock |4 to reinforce orbrace the'mountin'g for the cutterhead.

The arbor 34 projects upwardly within and bears against the innersurface of a bushing |42, which is press tted within the axial opening|30 through the cutterhead |28.

A head retainer tube |44 has the lower end thereof threadably receivedwithin the top of cutterhead |28, and is axially aligned with theopening therethrough. Such tube is mounted upon a forward projection|46, which is formed integral 'ring portion |12. It will thus be seenthat by ad- Justing the nuts |18, the member |86 may be verticallyadjusted with respect thereto.

The member |68 has an annular base portion which Vis'formed with aninner conical surface |18 and a vertical peripheral surface |80. A

Y back-off cone |82 is iixedly mounted to the head cone |66 and has adepending portion which is spaced from and substantially parallel to thevconical surfaces |18. It will thus be seen that the tion |38 in spacedrelation thereto. The tube |44 has a flexible ,tube |48 connectedthereto, and such tube leads to the outlet |50 of a pump |52 (see Fig.l), the inlet for such pump communicating through a suitable conduit |54with a supply of cutting oil. The pump is driven by-a suitable motor|58; and it will be appreciated that the cutting oil is thereby suppliedtube |44 and flows downwardly through the grooves 48 formed in arbor 34and flows over the cutters and blank during the cutting operations.V

Suitable control means for operating the motor |56`are indicated at |58.

A cutterhead support |80 is provided which has an axially extendingopening through which the tube |44 extends; and such member |60 bearsagainst the under surface of the projecting head stock portion |46. Themem er |80 is provided with a recess |62, which r eives a projectingportion |64 of cutterhead I2 'I'he under surface of member |60 isprovided with radial slots which receive radial projections formed onthe top surface of cutterhead |28, so that there is interlockingengagement between members |60 andy |28, so that the-cutterhead is fixedagainst rotation with respect to the axis of reciprocation of the work.The member-|60 is bolted to portion |48.

It will thus be seen `that the cutters ||8 are free to slide radiallywithin grooves |26 with respect to the cutterhead |28 and with respectto the gear blank 32, but are fixed against rotative or axial movementwith respect thereto.

Means are provided for controllably feeding the cutters I6 radiallyinwardly and backing such cutters off with respect to the gear blank 32in timed relation l to the reciprocable and rotary movement of ram 50,which carries gear blank 32 thereon.. Such mean/sf includes a head cone|68, which is hollow inform and which has a vertical tubular portion|88, which embraces-the 4upper end of the head stock |28. Tubularportion |68 is externally threaded and is disposed within an axiallyaligned ppening |10, formed in the lower upwardly projecting tail at therear end of each of the cutters llt` extends within the space betweenthe .conical surface |18 and the outer surface of member |82 so that theback edge |22 of cutters ||8 slidably bears against the conical surface|18. The next adjacent edge of slot |24 lidabLv bears against the outersurface of4 cone It will thus be appreciated that by vertically movingthe member |66 together with the member |82, that the cutters ||6 areradially moved with respect to the cutter head and the work.

The head cone |66 is guided in such vertical movement by means ofradially adjustable bearings |84, which may be circumferentially spacedabout the member |88 and may be slidably mounted within recesses formedin ring portion |38. The members |84 may be adjusted by means of wedgescrews |88, which are threadably received within tapped openings inmember |38 and which have wedge portions engaging complementary wedgeportions formed on members |84. Lock nuts v|88 may be provided for xingthe wedge screws |86 so as to maintain alignment of member |88 duringits vertical up and down movement.

The vertical movement of member |66 is effected by vertically moving thefeed connections |14. A Such feed connection |14 is in general arectangular frame element having a'pair of spaced and vertical sideswhich are integral-with the annular portion |12 adjacent the bottomthereof,I and which are connected at the top by a cross member having anintegral vupwardly extending portion |90.

The portion |90 forms a back-off connection which is slidably mountedfor vertical movement upon the front face of a feed plate |92. Themember |90 may be so slidably` mounted by means of vertically extendinggibs |94 which are fixed to the plate |92 and form ways within which themember |90 slides. The feed plate |92` is also mounted for verticalsliding movement on the front face |96 of head stock member I4; and suchmember is slidably fixed with respect thereto by means of verticallydisposed gibs |98, which are xed to the member I4 and form ways withinwhich the member 92 slides. It will thus be seen that the plate |92 isvertically and slidably ring-shaped portion |12 of feed connection |14.75

disposed with respect to member |4, and that the back-off plate isvertically and slidably disposed with respect to the feed plate |92.

B y moving the plate |92 downwardly in timed relation to thelreciprocable movement of the ram 50, it will be seen that the member|86 is correspondingly moved downwardly, and that the cutters ||6are'fed radially inwardly. Means are provided for effecting suchdownward movement, and means are also provided for effecting upwardmovement of the back-off plate |90 with respect to the plate; |92alternately with the down feed of plate |92 so that the cutters IIB arefirst fed radially inwardly by the downward movement of plate |92 andare alternately backed off in outward radial movement by upward movementof back-off plate |90. During cutting engagement of the cutters ||6 withthe blank 32, the back-off plate |90 is locked in its position withrespect to plate |92.

To accomplish these movements, a cam shaft holder is xedly secured tothe front face of member |92 adjacent the top thereof and is providedwith a bore for the reception of a cam shaft 202. A feed mechanismratchet wheel 204 is keyed to the forwardly projecting end of shaft 202;and a cam 206 is keyed to the inwardly projecting end of shaft 202. Acam follower 208 is fixedly connected to the upper end of member I4 andis so disposed that the follower portion 2 I0 thereof bears against thecam surface of cam 206. It will thus be seen that as the ratchet' wheel204 is rotated, the cam 206 is correspondingly turned so that the plate|92 is moved downwardly with respect to member |4. The cam 206 is soshaped as to provide the desired rate of downward feed, and at the endof one complete revolution it will be appreciated that the follower 2|0passes beyond cam portion 2|2 so that the plate |92 may be returned toits uppermost position. The cam is so designed that for one completerevolution thereof a complete gear [is formed, so that all ofy theinterdental space between the teeth to be cut is removed.

Means are provided for resiliently urging the plate |92 upwardly so thatthe cam 206 and cam follower 2|0 are in constant engagement with eachother. Such means include a pair of oppositely disposed bolts 2|4, whichare xed to supporting brackets 2|6 xedly secured to the front lface ofmember |4. Such bolts 2|4 are slidably received through openings formedin side projections 2| 8 formed integral with plate member |92; andVcompression springs 220 are disposed between brackets 2|6 andprojections 2|8 so that the plate member |92 is resiliently urgedupwardly. It 'will thus be seen that at the completion of one cycle,when the follower 2I0 passesbeyond cam portion 2I2, the plate member |92is returned to its uppermost position by means of the compressionsprings 220.

A feed cross head guide 222 is xedly secured to the front face of member|92 and has a vertical side face 224 against which an adjacent side ofplate member |90 slidably bears. A cross head 226 is slidably mountedwith respect to the guide 222. A feed ratchet rod 228, having a pawl 230mounted on one end thereof, is slidably received through an openingformed in guide 222 and is adjustably fixed to the upper end of crosshead 226. A back-off cam rod 230 is flxedly connected to the crosshead226 and is slidably received within a guide opening formed in guide 222.The projecting end of rod 222 is upwardly offset, as indicated at 232,to provide back off cam surfaces. 'I'he top and bottom surfaces of suchprojection are flattened and are engaged on both sides by back off rolls234, which are mounted upon studs and fixed to vmember |90. A feedlocking rod 236 is fixed to the cross head -226 and is slidably receivedwithin a guide opening formed in guide 222. A transverse opening 236 isformed in member |90 and is adapted to be aligned with the opening 222through which the rod 236 passes when the slide |90 is in onepredetermined position, so that the lock rod 236 may pass into suchopening 230 and lock the member |90 with respect to member |92. It willthus be appreciated that as the crosshead 22s is moved to the right(viewing Fig. 2), che pawl 230 engages one of the notches in the ratchetwheel 204, so that such ratchet wheel is turned counterclockwise,thereby moving the feed slide |92 downwardly through action of cam 206.As the cross head 226 is'moved to the left (viewing Fig. 2), the camsurfaces of oset portion 232, through engagement with rollers 234, causethe slide |90 to move downwardly with respect to plate |92, so thatopening 238 is aligned with rod 236 and passage of such rod into theopening locks the member |90 with respect to the slide plate |92,thereby locking these plates during# the cutting period. Movement' ofthe cross head 226 `to the right releases such locking engagement andcauses the slide plate |90 to move upwardly by the action of offsetportion 232, so that the cutters are backed off from engagement with thework.

The reciprocable movement of the crosshead 226 is effected in timedrelation with the reciprocation of ram 50, so that during upwardmovemerit of the ram the members |390 and |92 are locked with respect toeach other, and at the end` of such vertical reclprocation the cuttersareA backed o from their innermost position so that as the ram is moveddownwardly the cutters do not engage the stock, and at the end of suchdownward movement the ratchet wheel 204 is turned so as to effectinwardradialfeed of the cutters for the next succeeding out; It willthus be seen that the cutters are fed inwardly step by Step, andalternately backed off so that all ofthe teeth of the gear arecompletely formed for one complete revolution of the cam 206. It will beappreciated that by adjusting rod 228, that the feed may be varied.

The means for operating the crosshead in timed relation to thereclprocation of the ram includes a crosshead tongue 240. which is fixedto the crosshead 226 and which has a link 242 pivotally connectedthereto. The opposite end of the link is pivotally connected to one endof a lever` arm 244; and the opposite end of such lever arm is keyed toa shaft 246. Such shaft 246 is rotatably mounted within a feedbracket248, which is mounted upon standard I0. The opposite end of such shaft246 isfflxedly connected to a lever 250. The opposite end of such lever250 is pivotally connected to an upwardly -extending feed mechanism link252, which is so to one end of a lever 254; and the opposite end of suchlever 254 is xedly connected to a feed mechanism shaft 256. Such shaft256 is mounted within suitable bearing brackets 258, which may be fixedto the standard I0. The opposite end of the shaft is keyed to one end ofa lever arm 260, and the lower end of such lever arm ispivotallyconnected to a link 262. The opposite end of the crank link 262is pivotally connected through a. pivot pin 264` with one end of crank04. Such pin 264 is located o-center from the center of crank 04, andhas a predetermined position with respect .to the rotative "position ofthe crank so that the crosshead 226 is moved to the right or left in thedesired sequence with respect to the reclprocation of the ram.

Suitable control mechanism, such as that generally` indicated at 210,may be mounted at a convenient location for starting and' stopping theaardse? motor 9| for the purpose of operating the machine.

In the operation of the machine, the member Il may be moved verticallyupwardly through hand wheel l0, so that the arbor 34, with the machineelement or gear blank `32 mounted thereon, may be mounted on the ram.The member I4 may then be lowered to a predetermined vstarting positionby hand wheel 30. Back-up plate 212, having a vertically adjustablebolt' 214, is disposed above member Il, and the bolt 214 may then 'nepositioned to bear against the top of member Il to reinforce or back itup.

The motor 96 may then be started so that the ram is reciprocatedvertically and guided by the helical guides to move the blank toward andfrom the cutters IIS. Asmentioned above, the

.cutters are radially fed inwardly step by step and alternately backedoff in timed relation to the reciprocation of the ram through the feedmechanism, which is connected to the ram operating means.

Formal changes may be made in the specific embodiment of the inventiondescribed without departing from the spirit and substance of theinvention, the scope of which is commensurate with the appended claims.

What is claimed is: y

1. A machine for forming simultaneously a plurality of teeth in amachine element comprising a standard, a work holder, means mountingsaid holder for reciprocatory movement with respect to said standard, amounting member mounted on said standard to one side of said holder, a

feed plate mounted for sliding movement with respect to said membertoward and away from said holder, a back-olf plate slidably mounted withrespect to said feed plate, a cutter head having a plurality of radiallydisposed cutters mounted thereon for radial movement with respectthereto, means connecting said cutters to said back-off plate for movingsaid cutters radially with respect to said head upon movement of saidback-cd plate and said feed plate, and means for moving said feed plateand said back-oil plate in timed relation to the reciprocatory movementof said work holder.

2. A machine for forming simultaneously a plurality of teeth in amachine element comprising a standard, a work holder, means mountingsaid holderv for reciprocatory movement with respect to said standard, amounting member mounted yon said standard to one side of said holder, afeed plate mounted `for sliding movement with respect to said membertoward and away from said holder, a back-o plate slidably mounted withrespect to said feed plate, a cutter head having a plurality of radiallydisposed cutters mounted thereon, said cutters being mounted for radialmovement into and out of cutting engagement with the work mounted onsaid holder, means connecting said cutters to said backoff plate formoving said cutters radially with respect to said head upon movement ofsaid backoif plate and said feed plate, means for moving said feed platein timed relation to the reciprocatory movement of said work holder,means for locking said back-off plate with respect to said feed plateduring cutting engagement of said cutters with said work, and means formoving said back-off plate separately of said feed plate intimedrelationto the reciprocatory movement of said work holder.

3. In a machine for forming simultaneously a. plurality of teeth in amachine element in which a reciprocatory work holder moves the worktoward and from aplurality of circumferentially spaced radially disposedcutters, the combination with means for progressively feeding said cut-'l ters inwardly toward said element and alternately backing oi! saidcutters from saidr element," said last named means including a pair ofconea shaped elements fixed in spaced relation to each other andengaging said cutters, means axially l0 ilxing the position of saidcutters but permitting radial movement thereof, an axially movable feedplate, an axially movable back-oi! plate mounted on said feed plate,means connecting said backo plate to said cone elements, releasablemeans fixing said back-oir plate with respect to said feed plate so thatsaid back-off plate-may be axially moved separately from movement ofsaid feed plate or said back-oil plate and feed plate may be moved inunison to thereby move said cone-shaped members axially tofmove saidcutters radially outwardly or inwardly, and means for moving said feedplate and said back-ofi plate f in timed relation to the reciprocatorymovement of said work holder.

4. In a machine for forming simultaneously a plurality of teeth in amachine element .in which a reciprocatory work holder moves the work tofward and from a plurality of circumferentially spaced radially disposedcutterathe combination with means for progressively feeding said cuttersinwardly toward said element and alternately backing oi said cuttersfrom said element, said last named means including a pair of cone-shapedelements fixed in spaced relation to each other 3'5 and engaging saidcutters, means axially xing the position of said cutters but permittingradial movement thereof, an axially movable feed plate, an axiallymovable back-olf plate mounted on said feed plate, means connecting saidback-off plate to said cone elements, releasable means xing "saidback-off plate with respect to said feed plate so that said back-offplate may be axially moved separately from movement of said feed plateor said back-off plate and feed plate may be moved A'in unison tothereby move said cone-shaped members axially to move said cuttersradially outwardly `or inwardly, and means for moving said feed plateand said back-olf plate in timed relation t0 the reciprocatory movement5l of said work holder, and means for bodily, axially moving saidcutters, said cone-shaped members, said back-o plate and said feed platewith respect to said work holder.

5, A machine for forming simultaneously a plurality of teeth in amachine element comprising an upright standard, a work holder, meansmounting said work holder for vertical reciprocatory movement withrespect to said standard, a mounting member mounted on said standardabove said holder, a feed plate mounted for sliding movement withrespect to said member toward and away from said holder, a back-offplate slidably mounted with respect to said feed plate toward and awayfrom said holder, a cutter head xably mounted on said member, saidcutter head having a plurality of radial1y disposed cutters mountedthereon, said cutters being vfixed against axial movement with respectto said cutter head but being mounted for radial movement with respectthereto for movement into and out of cutting engagement with the workmounted on said work holder, means connecting said cutters to saidback-off plate for moving said cutters radially with respect to saidhead upon movement of said back-oil! plate and said feed plate, meansfor moving said feed plate in timed relation to the reciprocatorymovement of said work holder, means for locking said back-off plate withrespect to said feed plate during engagenient of said cutters with saidwork, and means for moving said back-off plate separately from said feedplate in timed relation to the recipv rocatory movement of said workholder.

6. A machine for forming simultaneously a plurality of teeth in amachine element comprising a standard, a work holder, means mountingsaidA holder for reciprocatory movement with respect to said standard, amounting member mounted on said standard to one side of said holder, afeed plate mounted for sliding movement with respect to said member formovement toward and away from said holder, a back-off plate slidablymounted with respect to said feed plate mounted for movement toward andaway from said holder, a cutter head fixed to said member, said cutterhead having a plurality of circumferentially spaced, radially disposedslots therein, the side walls of each of said slots being substantiallyparallel to each other and being disposed at a predetermined angle tothe axis of movement of said work holder, a cutter disposed in each ofsaid slots, means nxing said cutters, against axial movement withrespect to said cutter head but permitting radial movement with respectthereto for movement into and out of engagement with the work mounted onthe work holder, and means for feeding said cutters radially inwardlyand outwardly with respect to said element.

7. A machine for forming simultaneously a plurality of teeth in amachine element comprising a standard, a work holder, means mountingsaid holder for reciprocatory movement with respect to said standard, amounting member mounted on said standard to one side of said holder, afeed plate mounted for sliding movement with respect to said member formovement toward and away from said holder, a back-off plate slidablymounted with respect to said feed plate mounted for movement toward andaway from said holder, a cutter head Lxedly mounted to said member, saidcutter head having a plurality o f circumferentially spaced, radiallydisposed slots therein, the side walls of each of said slots beingsubstantially parallel to each other and being disposed at apredetermined angle to the axis of movement of said work holder, acutter disposed in mounted to said member. said cutter head having aplurality of circumferentially spaced, radially -disposed slots therein,the side walls of each of said slots being substantially parallel toeach other and being disposed at a predetermined angle to the axis ofmovement of said work holder,

Y a cutter disposed in each of said slots, means fixing said cuttersagainst axial movement with respect to said cutter head but permittingradial movement with respect thereto for movement into and out ofengagement with the work mounted on the work holder, and common meansfor reciprocating said work holder and for moving said feed plate andsaid back-olf plate so that said cutters are moved into and out ofengagement with said element in a predetermined sequence.

9. A machine for forming simultaneously a plurality of teeth in amachine element, comprising a standard, a work holder, means mountingsaid work holder for reciprocatory movement with respect to saidstandard, a mounting member mounted on said standard to one side of saidholder, a feed plate mounted for sliding movement with respect to saidmember for movement toward and away from said holder, a vback-olf plateslidably mounted with respect to said feed plate for movement toward andaway from said holder, a`cutter head fixedly mounted on said member,said'cutter head being provided with a plurality of circumferentiallyspaced, radially disposed slots therein at one end thereof, a cutterdisposed within each of said slots, an annular member mounted on saidmounting member and engaging said cutter head adjacent said cutters tohold said cutters against axial movement with I respect to said cutterhead but permitting radial each of said slots, means fixing said cuttersagainst axial movement with respect to said cutter head but permittingradial movement with respect thereto for movement into and out ofengagement with the work mounted on the work 2 holder, means connectingsaid cutters to said back-oil plate for moving said cutters radiallywith respect to said head upon movement of said back-off plate and saidfeed plate, means for moving said feed plate in timed relation to thereciprocatory movement of said work holder, and means for moving saidback-off plate separately from said feed plate in timed relation to thereciprocatory movement of said work holder.

8. A machine for forming simultaneously a plurality of teeth in amachine element comprising a standard, a work holder, means mountingsaid holder for reciprocatory movement with respect tosaid standard, amounting member mounted on said standard to one side of said holder, afeed plate mounted for sliding movement with respect to said member formovement toward and away from said holder, a back-off plate slidablymounted with respect to said feed plate mounted toward movement withrespect thereto, means connecting said cutters to said back-off platefor moving said cutters radially with respect to said head upon movementof said back-off plate and said feed plate, means for vmoving-said feedplate in timed relation to the reciprocatory movement of said workholder, and means for moving said back-off plate separately from saidfeed plate in 7 timed relation to the reciprocatory movement of saidwork holder.

10. A machine for forming simultaneously a plurality of teeth in amachine element, comprising a standard, a work holder, lmeans mountingplate slidably mountedwith respect to said feed plate for movementtoward and away from said holder, a cutter head nxedly mounted on saidmember, said cutter head being provided with a plurality ofcircumferentially spaced radially disposed slots therein at one endthereof, a cutter disposed within each of said slots, an annular membermounted on said mounting member and engaging said cutter head adjacentsaid cutters to hold said cutters against axial movement with respect tosaid cutter head but permitting radial movement with respect thereto,means connecting said cutters to said back-olf plate for moving saidcutters radially with respect to said head upon movement of saidback-off plate and said feed plate, means for moving said feed plate intimed relation to the reciprocatory movement of said work holder, andmeans for locking said back-off plate with respect to said feed plateduring engagement of said cutters with said work.

11. A machine for forming simultaneously a plurality of teeth in amachine element comprising a standard, a work holder, a means mountingsaid work holder for reciprocatory movement with respect to saidstandard, a mounting member mounted on said standard to one side of saidholder, a feed plate mounted for sliding movement with respect to saidmember for movement toward and away from said holder, a cutter headi'ixedly mounted on said member, said cutter head having a plurality ofradially disposed cutters mounted thereon, said cutters being fixedagainst axial movement with respect to said cutter head but beingmounted for radial movement with respect thereto for movement into andout ofy cutting engagement with the work mounted on the work holder,means connecting' said cutters to said feed plate for moving saidcutters radially with respect to said head upon movement of said feedplate, and means for moving .said feed plate in timed' relation to thereciprocatory movement of said work holder.

12. A machine for forming simultaneously a plurality of teeth in amachine element comprising a standard, a work holder, means mountingsaid work holder for reciprocatory movement with respect to saidstandard, a mounting member mounted on said standard to one side of saidholder, a feed plate mounted for sliding movement with respect to saidmember for movement toward and away from said holder, a cutter headxedly mounted on said member, said cutter head having a plurality ofradially disposed cutters mounted thereon, said cutters being xedagainst axial movement of said cutter head but being mounted for radialmovement with respect thereto for movement into and out of cuttingengagement with the work mounted on the 'work holder, means connectingsaid cutters to said feed plate for moving said cutters radially withrespect to said head upon movement of said feed plate, means for movingsaid feed plate in timed relation to the reciprocatory movement of saidwork holder, said last named means including a cam member mounted onsaid feed plate and engaging said mounting member, and means forindexing said cam in timed relation to the reciprocatory movement ofsaid work holder, so that said feed plate is moved towards said workholder a predetermined amount for each cycle of reciprocation of saidwork holder.

13. A machine for forming simultaneously a plurality of teeth in amachine element comprising a standard, a work holder, means mountingsaid work holder for reciprocatory movement with respect to saidstandard, a mounting member mounted on said standard to one side of saidholder, a feed plate mounted for sliding movement with respect to saidmember for movement toward and away from said holder, a back-oi! plateslidably mounted with respect to said feed plate for movement toward andaway from said holder, a cutter head fixedly mounted on said member,said cutter head having a plurality of radially disposed cutters mountedthereon, said cutters being fixed against axial movement with respect tosaid cutterhead but being mounted for radial movement with respectthereto for movement into and out of cutting-engagement with the workmounted on the work holder, means connecting said cutters to said. feedplate for moving said cutters radially with respect to said head uponmovement of said feed plate, means for moving said feed plate in timedrelation to the reciprocatory movement of said work holder, said lastnamed means including a cam member mounted on said feed plate andengagingsaid mounting member, and means for indexing said cam in timedrelation to-the reciprocatoryv movement of said work holder, so thatsaid feed plate is moved towards said work holder a predetermined amountfojr each cycle of reciprocation of said work holder.

14. A machine for forming simultaneously av plurality of teeth in amachine element comprising a standard, a work holder, means mountingsaid holder for reciprocatory movement with respect to said standard, amounting member mounted on said standard to one side of said holder, aleed plate mounted for sliding movement with respect to said member formovement toward and away from said holder, a back-ofi 'plate slidablymounted with respect to said feed l therein, the side v'alls of each ofsaid slots being' disposed at a predetermined angle to the axis ofmovement of said work holder, said angle being dependent upon theoutside helix angle of the' teeth to be cut in the machine element, acutter disposed in each of said slots, means fixing said cutters againstaxial movement with respect to said cutter head but permitting radialmovement with respect thereto for movement into and out of engagementwith the work mounted on the work holder, and means for feeding saidcutters radially inwardly and outwardly with respect to said element.

15. A machine for forming simultaneously a plurality of teeth in amachine element comprismg a standard, a work holder, means mounting saidholder for reciprocatory movement .with respect to said standard, amounting member mounted on said standard to one side of said holder, afeed plate mounted for sliding movement with respect to said memberformovement toward and away from said holder, a back-off plate slidablymounted with respect to said feed plate mounted for movement toward andaway 'from said holder, a cutter head fixed to said member,- said cutterhead having a plurality of circumferentially spaced, radially disposedslots therein, the side walls of each of said slots being disposed at apredetermined angle to the axis of movement of said work holder, saidangle being substantially the same as the outside helix angle of theteeth to be cut in the machine element, a cutter disposed in each ofsaid slots, means xing said cutters against axial movement with respectto said cutter head but permitting radial movement with respect theretofor movement into and out of engagement with the work mounted on thework holder, and means forfeeding said cutters radially inwardly andoutwardli with respect to said element.

16. A cutter head body for use in a machine for forming simultaneously aplurality of teeth in a machine element comprising a member having acentral axial opening therethrough, a plurality of circumferentiallyspaced. substantially radially disposed slots formed in one end thereofand directed toward said central opening, the v

